Intravenous Ondansetron and the QT Interval in Adult Emergency Department Patients: An Observational Study

Ondansetron is known to cause QT interval prolongation, but this effect and clinical significance has not been prospectively studied in adult emergency department (ED) patients. The primary objective was to determine the mean maximal corrected QT interval (QTc) prolongation after intravenous (IV) administration of 4 mg of ondansetron. The secondary objective was to report any serious adverse cardiac electrical events.

This was a prospective, observational, single-center cohort study conducted between 2012 and 2013 in an academic, military hospital ED. Adult patients ordered to receive 4 mg of IV ondansetron were eligible for the study. A six-lead electrocardiogram was recorded at baseline and every 2 minutes after ondansetron administration for 20 minutes. The QTc was calculated using the Bazett formula. Serious adverse cardiac electrical events (nonsinus rhythm, severe bradycardia, and sudden cardiac death) were also recorded.

Twenty-two adult ED patients were enrolled. Ondansetron caused a mean prolongation of the QTc by 20 ms (95% confidence interval [CI] = 14 to 26 ms), with a mean proportion change from baseline of 5.2% (95% CI = 3.8% to 6.6%). There were zero (95% CI = 0 to 13%) reported serious adverse cardiac electrical events.

While QTc prolongation does occur in adult ED patients receiving IV ondansetron, the clinical impact is questionable.